The present invention relates broadly to directional flow control valves for diverting the flow of a working fluid between two or more fluid flow paths, and particularly to a four-way valve of such variety adapted for use in heat pump systems and other reversible refrigeration cycles for reversing the direction of refrigerant flow in the circuit loop to alternately heat or cool the environment being controlled by the cycle.
Air conditioning and other refrigeration systems are operated in a thermodynamic cycle which conventionally may employ in series, as is shown at 10 in FIG. 1, a compressor, 12, a first heat exchanger 14, which may be an outdoor condenser, an expansion function, represented at 16, and a second heat exchanger, 18, which may be an indoor evaporator, all of which are arranged in a closed-loop circuit. Within such circuit 10, a refrigerant medium is cycled therethrough for its alternate conversion from a partially liquid state to a partially gaseous state effecting a conversion of heat to kinetic energy.
When operated in a conventional cooling mode, energy is supplied into the thermodynamic cycle via the compressor 12 which is operated as having a low pressure inlet or suction side, 20, and a high pressure outlet or discharge side, 22. Within the compressor, the refrigerant is compressed and super-heated to exit the outlet side 22 thereof via line 24 at a relatively high pressure. The refrigerant next is passed via line 25 through the first heat exchanger 14 wherein a heat transfer is effected with a lower temperature fluid to remove the heat of compression from the refrigerant for its further cooling. From the first heat exchanger 14, the flow of the refrigerant, which is now in a liquefied and pressurized state, is regulated by the expansion function 16 and then is passed into the second heat exchanger 18. The refrigerant within the second heat exchanger 18 is volumetrically expanded with a state change from a high to a low pressure liquid, and subsequently a phase change to a low pressure gas. The specific and latent heats associated with the state and phase changes of the refrigerant effect the cooling of the area surrounding the second heat exchanger 18 or, with forced convective systems, of a higher temperature cooling medium such as air which is circulated in a heat transfer relationship with the heat exchanger. From the second heat exchanger 18, the refrigerant, now in a relatively low pressure gaseous phase, is returned via lines 26 and 27 to the suction side 20 of the compressor 12 wherein it is again compressed and thereafter cooled for the repetition of the cycle.
However, and as is detailed in U.S. Pat. Nos. 3,867,960; 3,894,561; 3,992,898; 4,406,306; 5,186,021; and 5,341,656, refrigeration systems of the above-described type also may be operated in an alternate thermodynamic or "heat pump" cycle to additionally heat the working environment. When operated in such mode, the duty of the two heat exchangers typically is reversed thermodynamically by physically reversing the direction of the flow of refrigerant through the system, i.e., from the compressor discharge side 22 to the second heat exchanger 18 via lines 24 and 26, and then to the first heat exchanger 14 and returning to the compressor suction side 20 via lines 25 and 27. In this regard, and as is shown at 30 in FIG. 1, a multi-position, flow reversing control valve may be coupled in fluid communication with the suction and discharge sides of the compressor to selectively connect the heat exchangers to alternate sides of the compressor such that the first heat exchanger may be operated in a cooling or evaporator mode, with the second heat exchanger being operated in a heating or condenser mode.
To complete the thermodynamic reversal of the cycle, the refrigerant within circuit 10 must be throttled in the opposite direction through the expansion device. Therefore, the expansion function of such circuits conventionally may employ a double expansion device arrangement wherein a pair of expansion devices, referenced in FIG. 1 at 16a-b, are positioned in opposition within a supply line, 32, extending between heat exchangers 14 and 18. That is, devices 16a-b are arranged to throttle refrigerant in opposite directions. Expansion devices, which encompass capillary tubes, thermostatic expansions valves, and orifice piston-operated check valves, are further described in U.S. Pat. Nos. 5,695,225; 5,564,754; 5,553,902; 5,460,349; 5,390,897; 5,341,656; 5,295,656; 5,131,695; 4,674,673; 4,643,222; 3,992,898; 3,877,248; 3,745,787; 3,120,743; and D341,409. Further, it is common practice to distribute the refrigerant discharged from each of the expansion devices 16 into a plurality of different circuit tubes, one of which is referenced at 34a for device 16a, and at 34b for device 16b, each of which is connected to a different section of the corresponding heat exchanger coil.
A representative flow reversing or control valve of the general type herein involved is disclosed in U.S. Pat. No. 4,318,425 as including a valve housing defining a chamber in which a bearing surface is disposed with refrigerant port openings in the bearing surface. A valving member is slidably disposed on the bearing surface for selective communication with desired ports.
Another flow valve is disclosed in U.S. Pat. No. 4,644,760 as including a cylindrical valve body through which a single piston is adapted to slidably reciprocate in a differential pressure arrangement. The piston divides the valve body into two chambers, one of which is used for admitting high pressure gas thereinto, and the other of which is used for controlling the piston in counteracting the high pressure gas. A spring is used to urge the piston toward the high pressure chamber.
U.S. Pat. No. 4,573,497 discloses another refrigerant flow valve which includes a tubular valve body defining fluid ports. A valving member is supported by the body for movement with respect to the ports to direct refrigerant flow into different flow paths. Refrigerant flow tubes are hermetically fixed to the valve body for directing the refrigerant flow from the refrigeration system through the valve body. A heat transfer blocking structure is used to provide a high thermal impedance conductive heat transfer path through and along the valve flow tubes for minimizing heat transfer between the refrigerant and the flow tube walls.
U.S. Pat. No. 3,032,312 discloses a valve having a chamber with a plurality of adjacent fluid ports and a recessed slide member which is selectively slidable over certain ports to open and close alternate fluid passages. The slide member comprises a shell-like structure having a flexible, low-friction seal surrounding an open edge and presenting a fluid-tight surface for engaging the port area of the valve chamber. The shell is formed of two separate elements having rim sections which are shaped to mechanically secure the seal to the shell. Concave surfaces of the elements are spaced-apart intermediate the rim edges to provide a heat exchange barrier.
U.S. Pat. No. 5,074,329 discloses a three-way valve for a refrigeration system in which flow is alternately directed from a compressor to a condenser or an evaporator. The valve includes a valve body portion which defines fluid ports and an internal, elongate cavity. A cylindrical cartridge is disposed within the cavity and is movable therein to provide first and second operative positions. A pressure limiting or equalizing check valve is coaxially carried by the cartridge for limiting back pressure build-up.
U.S. Pat. No. 4,324,273 discloses a valve construction having a housing that is provided with a movable valve unit member. The valve member is interconnected to a piston unit having opposed piston heads that define a main chamber of the housing. The housing has opposing ends, each of which defines a control chamber which a respective one of the piston heads and has a valve seat leading to one of the control chambers. Each piston head has a flexible seal member which is adapted to close a valve seat defined by a respective end of the housing.
U.S. Pat. Nos. 4,448,211 and 4,432,215 disclose three-way valve constructions of a pressure-differential variety for use in refrigeration systems. The valve constructions include a control mechanism which is disposed within a main valve body. The control mechanism is provided for bringing a first valve in contact with a first valve seat of the valve body when the pressure within a first valve chamber is higher than a pressure within an opposing second valve chamber, and for bringing a second valve in contact with a second valve seat of the valve body when the pressure within the second valve chamber is higher than the pressure within the first valve chamber.
U.S. Pat. No. 4,319,607 discloses a valve assembly which includes a housing having an elongated central passageway and a plurality of spaced ports and valve openings along the length thereof, with the valve openings providing communication between adjacent ones of the spaced ports. An elongated drive shaft, which is movable by a hydraulic pressure actuator between a resting position and an actuated position, is disposed on the drive shaft and is biased at its resting position by a spring disposed around the shaft. A plurality of free floating sealing elements are spaced along the shaft as separated by another spring disposed in the housing around the shaft. Each of the valve elements is disposed between a pair of adjacent valve openings and is movable to open or close the one of the valve openings by the movement of the shaft. In one embodiment, as the shaft is moved to open one of the valve elements, the other is maintained in a closed orientation until contacted by an enlarged portion of the shaft.
U.S. Pat. No. 3,335,756 discloses an automatic sequencing valve for directing a fluid flow sequentially to first and second outlets spaced longitudinally and differentially from a common inlet. The valve includes a valve body which defines the inlet and outlet ports and associated valve seats, as well as an internal chamber in communication with the ports. A pressure-responsive piston valve is received within the chamber and is movable therein into and out of engagement with the valve seats thereby opening and closing the fluid ports. A stem additionally is received within the body as operably connected to the piston for movement therewith to open and close one of the valve outlets. A capillary tube may be provided in communication with opposite ends of the chamber for imposing a time delay on the motion of the stem relative to the motion of the piston.
U.S. Pat. No. 3,225,557 discloses a three-way valve which includes a body portion having a cylindrical chamber, and compressor discharge, compressor suction, and evaporator ports opening into such chamber. The valve also includes a piston which is movable within the chamber for controlling fluid communication between the ports, and a solenoid for controlling the movement of the piston.
U.S. Pat. No. 3,894,561 discloses a four-way reversing valve for refrigeration systems. Within the valve, a three-way pilot valve is employed to control application of high or low system pressure to the end of chamber which is adjacent the larger end of a double-headed, differential area piston.
U.S. Pat. No. 3,867,960 discloses a five-way reversing valve wherein the flow direction of two pressurized fluid streams can be simultaneously changed by way of a pressure differential between the two fluids. The flow directions are changed by the combined operations of an elastic coil spring and a slidable plunger whose movement is controlled by the spring.
U.S. Pat. No. 4,406,306 discloses a switch-over valve for use within a heat pump system. The valve includes a body having discharge and suction ports for interconnection with the heat pump compressor, and two reversing valve ports for interconnection with the heat pump coils. The valve further includes a solenoid-operated pilot valve, a slave valve for selectively interconnecting the discharge port with one of the reversing valve ports, and a shuttle poppet valve for interconnecting the suction port with the other reversing valve port.
Other flow control valves and refrigeration systems are described in U.S. Pat. Nos. 2,780,077; 3,738,573; 4,026,320; 4,087,986; 4,112,974; 4,144,905; 4,212,324; 4,213,483; 4,237,933; 4,241,486; 4,248,058; 4,255,939; 4,292,720; 4,311,020; 4,492,252; 4,573,497; 4,712,582; 4,791,960; 4,825,908; 5,026,022; 5,048,791; 5,299,431; 5,309,731; 5,316,074; 5,386,704; and 5,507,315, and in and in Int. Publ. No. WO 96/00664.
The above-described references have constituted the state of the art with respect flow control switching, sequencing, reversing, or diversion valves for heat pumps and other refrigeration systems. It is believed, however, that further improvements in flow reversing valves for such systems continue to be desired by manufacturers. In this regard, a preferred valve construction would be economical to manufacture, but additionally would be reliable, efficient, and compact so as to be easily incorporated in existing air conditioning system designs.